Ok, captain pedant, delete "few" or replace the name Prunier with any one of dozens of unsuccesful signings over the years and my point stands. The fact that Evra had a ropey first few games has no bearing on Diouf's ability as a footballer. Sure there's been good signings that didn't hit the ground running but almost every single bad signings is similarly inept in their first few outings.
Personally, I'm still hopeful about Diouf. I'd always rather see a striker get in positions to miss chances than not get chances at all. I do think he's absurdly over-hyped due to people taking all that daft "the one" stuff a bit too seriously and he looks raw as anything but he's obviously got potential.